[TimotheusG]

Dependencies and merge order

Independent; proposed landing position 4. This fixes baseline Windows viewer-harness interference; it supplies no runtime prerequisite to the audio/export PRs.

Full nine-PR index, merge instructions, audited heads and validation evidence. The first five positions are independent, not a serial dependency chain. Combined CI evidence is not a claim of nine standalone full-suite passes.

Full Windows CI intermittently terminated ui_viewer with 0xc0000005; Windows Error Reporting identified Microsoft d3d10warp.dll (10.0.26100.9711) as the faulting module. Running only the three shape_drag_ghost tests with 64 test threads also reproduced the native crash immediately.

A viewer-harness access violation was also reported in #1732, independently of the audio changes.

The default egui_kittest renderer lazily creates a separate wgpu render state for each harness and prefers software adapters. Serialize the four screenshot-rendering tests on Windows, holding a shared guard until their harnesses drop. The remaining viewer tests stay parallel, other platforms are unchanged, and no pixel assertions or tests are removed. This is a test-harness workaround for concurrent Windows software-renderer crashes, not a change to production graphics or audio behavior.

Validation: five repetitions of the formerly crashing three-test subset with 64 test threads, two complete 66-test viewer runs, then full cargo xtask ci on Windows all passed. Full CI: 3,683 passed, 0 failed, 33 existing/opt-in ignored; strict Clippy, formatting, audits, and 32 WebAssembly crates passed. The integration branch combines #1889, #1890, #1891, #1827 and #1915 (automatic-backend timing-test fix). This PR changes only ui_viewer.rs.

Summary by CodeRabbit

• Tests
  • Windows UI screenshot tests now run with serialized harness lifetimes to reduce interference and improve consistency.
  • Expanded checks verify that UI-only construction has no WGPU render state, wide-frame output can be read without rendering, and shape-drag operations produce the expected layers, groups, ghost results, and final layer position. No change to app behavior.

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• crates/ui-egui/tests/ui_viewer.rs

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📝 Walkthrough

The UI viewer tests add a Windows-only mutex guard for selected screenshot harnesses. They also check that UI-only contexts lack WGPU render state and verify committed shape and layer drag outcomes.

Changes: UI Viewer Test Updates

Layer / File(s)	Summary
Check UI-only render state crates/ui-egui/tests/ui_viewer.rs	The general and selection harnesses, and the wide-frame test, assert that no WGPU render state is present. The wide-frame test reads CPU output without calling render().
Serialize screenshot harnesses and check drag results crates/ui-egui/tests/ui_viewer.rs	Selected tests use a Windows-only mutex guard that recovers from a poisoned lock. Drag tests check committed shape contents, layer creation, and the final layer position.

Priority: ⬇️ Low

Estimated code review effort: 2 (Simple) | ~8 minutes

Change: Other

Suggested reviewers: claude

Merge Risk: ⚪ Minimal · up to ac787

The changes strengthen UI viewer tests and serialize Windows screenshot cases. No current-head regression is established, so merge risk is minimal after normal checks.

Pre-merge checks: 5

Check name	Status	Explanation
Description Check		Check skipped - CodeRabbit’s high-level summary is enabled.
Title check		The title clearly and concisely describes the main change: serializing Windows viewer screenshot harnesses in UI tests.
Docstring Coverage		Docstring coverage is 90.00% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 10 functions across 1 files.
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.

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Inline comments:
Review comments at @crates/ui-egui/tests/ui_viewer.rs:
- Line 491: Update tests using harness() or selection_harness() to retain
screenshot_guard() for the full lifetime of each WGPU-backed harness, and scope
the first harness in the shape-landing test so it is dropped before the second
is created. Keep non-WGPU tests unchanged.

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[TimotheusG]

Addressed the overlapping-device lifetime: the shape-landing test now explicitly drops its first screenshot harness before constructing the second. Added post-release shape/layer assertions and verified the final drag position.

I checked the installed egui_kittest 0.36.2 source: HarnessBuilder defaults to LazyRenderer; LazyRenderer does not override TestRenderer::setup_eframe and only constructs WgpuTestRenderer on render(). Therefore harness()/selection_harness() do not create a WGPU device just by building or stepping. The wide-frame test never calls render(); viewer_pixels uses its CPU frame. New assertions check that all three construction paths receive no WGPU render state. The four screenshot tests retain their Windows guard across the actual GPU lifetimes, while UI-only tests remain parallel.

Pushed in ac787fc. Final combined Windows cargo xtask ci: 3,683 passed, 0 failed, 33 unchanged ignored; formatting, strict Clippy, audits, and 32-crate WASM checks passed. An additional 64-thread ui_viewer run passed all 66 tests. Companion PR files are byte-identical to those validated in the combined audio branch.